The Organic Light Emitting Display (OLED) possesses many outstanding properties of self-illumination, low driving voltage, high luminescence efficiency, short response time, high clarity and contrast, near 180 degree view angle, wide range of working temperature, applicability of flexible display and large scale full color display. The OLED is considered as the most potential display panel.
The OLED display element generally comprises a substrate, an anode located on the substrate, a hole injection layer located on the anode, a hole transporting layer located on the hole injection layer, an emitting layer located on the hole transporting layer, an electron transporting layer located on the emitting layer, an electron injection layer located on the electron transporting layer and a cathode located on the electron injection layer. The principle of the OLED element is that the illumination generates due to the carrier injection and recombination under the electric field driving of the semiconductor material and the organic semiconductor illuminating material. Specifically, the ITO pixel electrode and the metal electrode are respectively employed as the anode and the cathode of the OLED element. Under certain voltage driving, the Electron and the Hole are respectively injected into the Electron and Hole Transporting Layers from the cathode and the anode. The Electron and the Hole respectively migrate from the Electron and Hole Transporting Layers to the Emitting layer and bump into each other in the Emitting layer to form an exciton to excite the emitting molecule. The latter can illuminate after the radiative relaxation.
The Ink-jet Printing (IJP) has advantages of high material utilization, which is the key of solving the cost issue of the large scale OLED display. In comparison with the traditional vacuum evaporation of prior art, the IJP skill possesses many advantages of material saving, gentle process condition and more uniform film formation and thus has more potential applications. The method is to drop the function material ink into the predetermined pixel areas with a plurality of nozzles. Then, the required pattern is formed after the solvent is evaporated.
The metal nanoparticles provide many excellent optical and electrical properties with their special volume effect, quantum size effect, surface effect and macroscopic quantum tunneling effect.